The present invention relates to a method for manufacturing, from a flat product in sheet form, a corrugated fin for a plate-type heat exchanger, of the type defining a main overall direction of corrugation and comprising at least one corrugation which is more or less transverse to the said main overall direction, the said corrugation having corrugation legs connecting corrugation crests and corrugation troughs, the said corrugation having a series of perforations.
FIG. 1 of the appended drawings depicts, in perspective, with partial cut away, one example of such a heat exchanger, of conventional structure, to which the invention applies. This may, in particular, be a cryogenic heat exchanger.
The heat exchanger 1 depicted consists of a stack of parallel rectangular plates 2, all identical, which define between them a number of passages for fluids to be placed in an indirect heat-exchange relationship. In the example depicted, these passages are, successively and cyclically, passages 3 for a first fluid, 4 for a second fluid and 5 for a third fluid.
Each passage 3 to 5 is bordered by closure bars 6 which delimit it, leaving inlet/outlet openings 7 free for the corresponding fluid. Placed in each passage are corrugated spacer pieces or corrugated fins 8 which act simultaneously as heat-exchange fins and as spacer pieces between the plates, particularly during the brazing operation and to avoid any deformation of the plates when pressurized fluids are used, and serve to guide the flow of the fluids.
The stack of plates, closure bars and corrugated spacer pieces is generally made of aluminium or aluminium alloy and is assembled in a single operation by furnace brazing.
Fluid inlet/outlet boxes 9, of semi-cylindrical overall shape, are then welded onto the exchanger body thus produced, to cap the corresponding rows of inlet/outlet openings, and are connected to pipes 10 for conveying and removing the fluids.
There are various types of corrugated spacer pieces 8 in existence, for example a simple perforated corrugated spacer piece such as the one depicted in FIG. 2.
Throughout the description, reference will be made to this type of simple perforated corrugation, it being clearly understood that the invention applies to many other more complex types of corrugation, for example of the xe2x80x9cserrated finxe2x80x9d or xe2x80x9cpartial offsetxe2x80x9d type in which, at regular intervals along the generators, the corrugation is offset transversely, generally by half a corrugation pitch, xe2x80x9cchevron corrugationsxe2x80x9d or xe2x80x9cherringbone corrugationsxe2x80x9d, with corrugated generators, xe2x80x9cslatted corrugationsxe2x80x9d, the legs of the corrugations of which exhibit lancings, etc.
The simple perforated corrugation has a main overall direction of corrugation Dl, the corrugations being oriented in a direction D2 perpendicular to the direction D1. In xe2x80x9cherringbonexe2x80x9d corrugations, D1 is taken to be the mean direction of the corrugation.
For the convenience of the description, it will be assumed that, as depicted in FIG. 2, directions D1 and D2 are horizontal.
The corrugation 8 has a crinkled shape and comprises a great many rectangular corrugation legs 12, each contained in a vertical plane perpendicular to the direction D2. With respect to an overall direction F of the flow of the fluid in the direction D1 in the passage in question, each leg has a leading edge 13 and a trailing edge 14. The legs are connected alternately along their upper edge by flat and horizontal rectangular corrugation crests 15 and along their lower edge by corrugation troughs 16 which are also rectangular, flat and horizontal.
Perforations 20 are made in the corrugation legs, so as to introduce turbulence into the flow of the fluid through the heat exchanger, and thus encourage heat exchange.
In order to manufacture corrugated fins of the type which has just been described, the general procedure is as follows: the perforations are made, using a perforating tool, in the flat product before it is bent, and the bends are made, using a bending tool, in the perforated flat product. These operations are carried out in succession and discontinuously, which means that the flat product is extracted from the first tool after perforation, and before being processed in the second tool, because processing the flat product continuously in the two tools is made difficult by the difference in speed of travel of the flat product corresponding to each of these two tools.
Furthermore, the slippage of the flat product in the bending tool after perforation and its elongation are difficult to control, and this gives rise to significant variations in the positioning of the perforations with respect to the bend.
This leads to thermal properties which are not very uniform and difficult to control. In addition, if the perforations are distributed over the entire surface of the flat product, the area of the contact between the corrugation crests and troughs, on the one hand, the adjacent plates 2 on the other hand, are not constant. In consequence, the resistance of the brazed connections to tearing out and the transfers of heat between the corrugations and the plates are not controlled.
With the prime objective of overcoming these drawbacks, the invention relates to a method of manufacture of the type described hereinabove, in which:
the product is made to pass step by step between the perforating tool and the bending tool, the relative position of the said tools being variable in the direction of travel of the flat product;
the position of a perforation on the corrugation is detected; and
the relative position of the tools is slaved to the detected position.
The invention also relates to a device for implementing a method as described hereinabove, comprising a perforating tool and a bending tool each having an entry and an exit, the assembly formed by the perforating tool and the bending tool constituting treatment line intended to process a flat product, characterized in that the treatment line processes the flat product continuously, the exit of the perforating tool being connected to the entry of the bending tool, and the relative position of the perforating tool and of the bending tool in the direction of travel of the flat product through the treatment line is adjustable via command and control means.
The invention additionally relates to the use of a method or of a device both as described hereinabove for producing corrugated fins of hybrid structure, in which perforations are arranged in spaced-apart transverse bands of the flat product, these bands being separated by non-perforated bands or alternatively for producing corrugated fins having notched offset corrugations on at least some leading edges and/or at least some trailing edges of the corrugation legs and possibly of the corrugation troughs and/or crests.